docs: def log(message, level=None):
      """Write a message to the juju log"""
      command = ['juju-log']
      if level:
          command += ['-l', level]
      if not isinstance(message, six.string_types):
          message = repr(message)
      command += [message[:SH_MAX_ARG]]
      # Missing juju-log should not cause failures in unit tests
      # Send log output to stderr
      try:
          subprocess.call(command)
      except OSError as e:
          if e.errno == errno.ENOENT:
              if level:
                  message = "{}: {}".format(level, message)
              message = "juju-log: {}".format(message)
              print(message, file=sys.stderr)
          else:
              raise